The transmission of a digital signal by inverse multiplexing makes it possible to utilize several parallel transmission links such as, for example, several parallel optical fibers with less bandwidth than that required for the transmission of the digital signal. In this case, the digital signal is divided into several subsignals that are respectively transmitted via one of the parallel transmission links from a transmitting end to a receiving end of the transmission links. On the receiving end, the subsignals are once again assembled into a digital reception signal with consideration of the correct sequence of the bits or bytes that were transmitted via different transmission links. Consequently, the transmission by inverse multiplexing makes it possible to continue using existing parallel transmission links (strictly speaking, the term “parallel” in this context is merely intended to convey that the individual transmission links have a common starting point on the transmitting end and a common end point on the receiving end), namely even if a digital transmission signal requires more bandwidth than that provided by each individual transmission link. If applicable, it is also possible to continue using existing transmitting units and receiving units of the individual transmission links, particularly the components that, for example, bring about a signal conversion or a signal conditioning of the individual subsignals.
With respect to the optical signal transmission via an Optical Transport Network (OTN), International Standard ITU-T G.709/Y.1331 defines how the transmission and signal processing at the interfaces on the transmitting end and the receiving end has to take place.
For the transmission by inverse multiplexing, the digital signal that corresponds to a certain service, such as, for example, an Optical-channel Transport Unit of the category 3 or 4 (OTU3 or OTU4 service) is split into individual parts, namely so-called Logical Lanes (LL), wherein a single or several LL can then be respectively combined into a subsignal. Each of the thusly generated subsignals can then be transmitted from the transmitting end to the receiving end via a respectively assigned transmission link. Since the propagation times of the individual subsignals can significantly vary in this case, the assembly of the subsignals into a digital reception signal that corresponds to the digital transmission signal requires a synchronization of the subsignals such that the individual blocks of bytes that are respectively assigned to an LL have the same sequence in the digital reception signal as in the digital transmission signal.